The invention relates to the technical field of wireless communication, and in particular relates to a method for recording the offline time of a user terminal based on RADIUS and PORTAL protocols. The method comprises the steps that: when being accessed to a hotspot covered by a first AP, the user terminal is authenticated through an authentication server; after the user terminal passes authentication, a PORTAL server writes the online time of the user terminal in a database server; when the online state of the user terminal is changed, the authentication server records the offline time of the user terminal in the database server; and simultaneously, the PORTAL server reads and updates an REDIS online user cache list. By means of the method for recording the offline time of the user terminal disclosed by the invention, the offline time of the user terminal can be recorded; therefore, complete online and offline logs are conveniently obtained; and operation and management of a wireless city are easily carried out.